Several known energy extracting (also referred as “harvesting”) devices generate electricity based on motion resulting from muscle actuation. Such energy extracting techniques are based on induction (e.g., geared motion into a generator) or piezoelectricity (e.g., pressure or vibrational motion of a piezoelectric material). For example, heel-strike or leg-mounted harvesters are used to extract energy from muscle actuation. Another form of energy extraction is based on temperature differences, e.g., between the temperature of atmosphere and a live animal.
Another approach to energy extraction relies on chemical reactions. Such systems extract energy from glucose that is naturally found in blood. One example is microbial biofuel cell technology, which use precious metals and whole-cells as catalysts. Another example is enzymatic biofuel cell technology, which uses enzymes as catalysts.